Addition products of sulfuric acid and polycarboxylic tertiary amino acids



Patented Dec. 1950 ADDITION PRODUCTS OF SULFURIC ACID AND POLYCARBOXYLIC TERTIARY AMINO ACIDS Frederick C. Bersworth, Verona, N. J.

No Drawing. Application October 4, 1947, Serial No. 778,046

1 9 Claims. 1

This invention relates to addition products of sulfuric acid and polycarboxylic tertiary amino acids. It is a continuation-in-part of my copending application Serial No. 491,670 filed June 21, 1943, issued on October 7. 1947 as U. S. Patent No. 2,428,353.

These addition products, as pointed out in said copending application, are of particular value in the formation of esters of said tertiary-amino acids, which esters and their preparation are claimed in that application. They are also useful for other purposes, such as in forming anhydrides, and as intermediate products in the formation of other compounds.

The preparation of addition products of primary and of secondary amino acids has already been described in the literature. These amino acids have respectively two and one hydrogen atoms attached directly to each amino nitrogen atom, and are relatively much more basic than tertiary amino acids, in which there are no hydrogen atoms attached directly to the amino nitrogen atoms. The addition of relatively strong mineral acids to primary amino acids has been found to take place fairly readily, due to the basicity of the latter. The addition of such mineral acids to secondary amino acids has been found to proceed with greater difficulty, due to the lesser basicity of the secondary amino nitrogens. On the other hand, the addition of such mineral acids to tertiary amino compounds having a plurality of carboxylic acid groups in the molecule, and being strongly acidic in character, has, as far as I am aware, been considered impossible, due among other things to the relative acidity of such tertiary amino acids. In fact, such tertiary amino acids which are amenable to the procedure of this invention have pH values in the order of pH=2.

It is therefore an object of thisinvention to prepare addition compounds of sulfuric acid and polycarboxylic tertiary amino acids. Another object is to prepare these addition compounds in an economical and practical manner, with good yields and relatively little formation of undesirable icy-products. Other objects will be apparent from the followin disclosure.

In carrying out the procedure of this invention, strong sulfuric acid is added to the polycarboxylic tertiary amino acid, in an amount such that there will be at least 1.1 hydrogen atom of the sulfuric acid present per tertiary amino nitrogen atom. A considerable excess of sulfuric acid over this proportion (e. g. twice as much) may be used. Much larger amounts are wasteful, and may lead to undesirable side reactions under some conditions of preparation, while smaller amounts than the minimum mentioned above result in poor or erratic yields. The pH value of the sulfuric acid should be distinctly in excess of that of the polycarboxylic tertiary amino acid to which it is added, e. g. the former shouldbe at least pH=l,

or preferably pH=O or even less, when the pH of the amino acid is about 2. And yet, surprisingly enough, the amino acids amenable to the procedure of this invention are not decomposed or otherwise deleteriously affected by such strong mineral acid treatment. Further details of the conditions of reaction for proper results will appear hereinafter.

The polycarboxylic tertiary amino acids with which this invention is concerned may be made, for example, in accordance with my U. S. Patent No. 2,407,645. They are, more specifically, N- polyacetic acids of alkylene (or polyalkylene) amines (or polyamines) wherein each nitrogen atom is bonded to one alkylene group and to two acetic acid groups, -CH2COOH (or to two of the former and one of the latter), and to no other groups or atoms. That is, each nitrogen atom is a tertiary nitrogen atom. Examples of these polycarboxylic tertiary amino acids, which are useful in carrying out the procedure of this invention to produce the addition products herein described and claimed, are the N,N'-tetraacetic acids of ethylene diamine, propylene 1,2-diamine, propylene 1,3 diamine, tetramethylene 1,4-diamine. and hexamethylene 1,6-diamine; the N,N,N"-pentaacetic acids of diethylene triamine and dipropylene 1,2-triamine; triethylene tetramine N,N,N",N" hexaacetic acid, and higher homologues thereof; ethyl amine N-diacetic acid, normal cc-bllllYl amine N-diacetic acid and other alkyl monoamine N -diacetic acids including those of the higher alkyl amines such as la'uryl and ste'aryl, and cyclohexyl amine N-diaceticacid. It will be noted that in all these compounds, the nitrogen atoms all occur in the configuration CH-N(CH2COOH)2 except that the nitrogen atoms intermediate a hydrocarbon chain occur in the configuration CHzCOOH In carrying out the process of this invention, there must be used, as already indicated, sufficient sulfuric acid to provide at least 1.1 atoms of acid hydrogen (of the sulfuric acid) per atom of amino nitrogen in the amino acid. Thus, per mol of mono amino acid, at least 0.55 mol of sulfuric acid are used; per mol of diamino acid, at least 1.1 mols of sulfuric acid; per mol of triamino acid, at least 1.65 mols of sulfuric acid; and so on. In actual practice, an excess of sulfuric acid over these amounts is preferred, in order to insure completion of the reaction and avoidance of any appreciable amounts of unreacted ingredients. Thus, a convenient working point is in the order of about 50% excess over theoretical, e. g. about 1.5 mols sulfuric acid per mol of diamino polycarboxylic acid. But even if considerable excesses of sulfuric acid are used, the final addition prod- 3 ucts, on analysis, are found to contain between about 1.1 and 2 mols of sulfuric acid per mol of diamino polycarboxylic acid (or,-per two mols of monoamino carboxylic acid, or per two-thirds mol of triamino carboxylic acid, etc.). These addi-. tion products are homogeneous compounds and are in the form of dry, or substantially dry, ,White crystalline powders, except that those of the higher alkyl monoamines such as lauryl and stearyl are rather of a soap-like feel and=fiaky nature than powdery. I, 1

The preparation of the addition product may be carried out by either a wet or a dry-7. process.

In the wet process, the sulfuric acid is added to theamino acid, in an amount within the range already set forth, and in such concentration ,to give a pH value of preierably about zero, or even less, to the resulting mixture. The sulfuric acid should thereforebe added in aqueous solution of atleast 1 N strength; and preferably highen'e. g. i N.,, The mixture is heated, preferablyto incipient or actual boiling -and preferably with refluxing if boiling takes piace-while the reaction to form the addition product. proceeds. Upon subsequent cooling, the addition product proceeds. Upon. subsequent cooling, the addition product crystallizes out, and may be removed as byfiltration, and then dried if desired. I

For example, take 2 mols concentrated (96%) H2804 in lit-U9 cc. water (he. about 4 N), and mix in one mol (292 g.) ethylene diamine N,N',tetraacetic acid; heat, with stirring, to incipient boil.- ing, whichproduces a clear solution. ,Thenv allow this solution to cool, whereupon crystals of the clesiredaddition product forn1... As the solubility gradient with temperature is steep, the colder the solution thebetter the yield. 'The crystals are filtered on and sucked as dry as possible. They are very clean, and filter well; washing is unnecessary and in fact is undesirable, as the addition product is water-soluble and is easily hydrolyzed- Hydroiysis may be employed for purposes of analysis in determining the amounts of sulfuric. acid and amino acid in the product; these arefound to be in the ratio of substantially 1.5 mols to lmol. i The same procedure may be followed, with like results, for the otherdiamino tetraacetic acids re ferred to above, e. g. thoseofpropylene 1,2-di.-. amine, hexamethylene diamine, etc. For the. monoarnino diacetic acids, the ratio of sulfuric acid employed to amino acid is conveniently about, one half that of the foregoing exampl (e. g. .f01-,-;. low that example but use 2 mols n-a butyl amine diacetic acid. For the triamino pentaacetic acids, the amount of sulfuric acid per mol of amino acid should be correspondingly increased,- e. g. follow the foregoing example but use 2.5 mols H2504 in 1250 cc. water with one mol diethylene triamine pentaacetic acid. 7

In the dry process, the dry crystalline amino acid is treated with substantially anhydrous (e; g. 96%) HzSCu, in the proper quantities; with thor.- ough stirring, amino acid takes up the liquid H2804 to form a substantially dry crystalline. powder. This procedure avoids the presence of extra water and the necessity for filtration and drying. On the other hand, the mixing must be givenrnore attention to assure that the resulting addition product is homogeneous. For example, use one mol of dry crystalline anhydrous diamino tetraacetic acid to between,

ill

., thatindicatediwiuresult in a moist or sloppy l productrdueito the presence of uncombined sulfuricac'id. .I claim:

1.An addition product consisting of a poly- .carboxylic-ater'tiary amino acid and sulfuric acid,

inthe ratio of at least 0.55 molecules of sulfuric acid; per nitrogen atom of said amino acid.

2. An addition product consisting of a tetracarboxylic. tertiary diamino acid and sulfuric acid, in-the ratioofatleast-Ll.molof sulfuric acid per mol of said diamino acid.

An addition product consisting of sulfuric acid and ethylene diamine N,N'.--tetraacetic acid, in the ratio of at least 1.1 mol of sulfurioacid per molofsaid diaminoacid. r

=4...An additionproduct consisting of sulfuric acid and propylene 1,2-diamine N,N-, -tetraacetic acid, in theratio of at least 1.1 mol of sulfuric acid per mol of. said cliamino acid.

5.. An additionproduct consisting of sulfuric acid and a dicarboxylictertiary mono amino acid, in the ratio of 0.55 mol of sulfuric-acid per molofsaidaminoacid; 1w

6. An addition product consisting of sulfuric acid and apentacarboxylictertiary triamino acid, in the ratio of at least 1.65 molsofsulfuric .acid

. per mol ofsaid triamino acid.

Lland 2 mols of sulfuric acid; or one mol of .the dry anhydrous monoamino diacetic acid tobe =7. Anaolditionxproductv consisting of sulfuric acid andv diethylene triamine pentaacetic acid, in the ratio of at least 1.65 mols-of-sulturic acid per mol ofsaid triaminoacid. t

.8. The method of-preparing an addition prod not of apolycarboxylictertiary amino acid andsulfuric acid; which comprises heating together a mixture of said aminoaacid. and sulfuric: acid" in the ratio of at'least0.55 moleculeiof .sulfurieacid perynitrogen atomof said amino acid; cooling the heated "mixture; and removing rthe resulting crystals'ofaddition productof said twoacidsl .9. The method of preparing amadditionprodnot which comprises heating-' together to sub stantially. the, boiling-pairing;- solutioniIof-a'at ileast l. N. sulfuric acid and ethylene GiaIn-ine N,N tetraacetic..acid,s=in thearatioof at least ll incl sulfuric acid permol'of said amino acid; cooling the resulting solution, and removing therefrom the resulting crystals of the addition product of said two acids. a

FREDERICK C. BE

witnessed s The following"references ar 'of 'record in the file ofthis'patentr"" OTHER REFE EuoEs Heintz: Liebigs"Annalenivolli336, 216, 219 (1865).. Heintz etc., Beilstein (4th ed.), vol. 4, pp. 370(1922). 

1. AN ADDITION PRODUCT CONSISTING OF A POLYCARBOXYLIC TERITARY AMINO ACID AND SULFURIC ACID, IN THE RATIO OF AT LEAST 0.55 MOLECULES OF SULFURIC ACID PER NITROGEN ATOM OF SAID AMINO ACID. 